1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a medium.
2. Description of the Related Art
In recent years, the tandem color image forming apparatuses have been increasing in number among the electrophotographic color image forming apparatuses, which comprises developing machines and photoconductor drums in the same number as that of toner colors and sequentially transfer images indifferent colors onto an image conveyance belt or onto a recording medium in order to implement a high speed of image formation. In the tandem color image forming apparatus, it is known that a plurality of factors that cause a deviation in registration exists and various methods for addressing each factor have been proposed.
As the factors that cause a deviation in registration, mention is made of unevenness and a deviation in the attachment position of the lens of the deflection scanning device, a deviation in the position of assembling the deflection scanning device to the main body of the color image forming apparatus, etc. Due to this deviation in position, the scanning line is inclined or curved and the degree of the curve and the direction of the curve of the scanning line differ for each color, and thereby, a deviation in registration is caused. Hereinafter, in the present specification, information on the scanning line, such as the degree and direction of the inclination and curve of the scanning line, is called a “profile”.
As a method for addressing a deviation in registration, Japanese Patent Laid-Open No. 2004-170755 describes the method in which the magnitudes of inclination and curve of the beam scanning line are measured by using an optical sensor, bitmap image data is corrected so as to cancel them, and a corrected image thereof is formed. By the method described in Japanese Patent Laid-Open No. 2004-170755, the image data is corrected electrically, and therefore, mechanical adjusting members and adjusting processes at the time of assembly are no longer necessary. Consequently, it is made possible to downsize the color image forming apparatus and at the same time, to address the deviation in registration at a low cost.
In recent years, the image forming apparatuses comprising multiple beams in order to implement a still higher speed of image formation have been increasing in number among the electrophotographic color image forming apparatuses. In this multibeam image forming apparatus, an image of each color plane is formed by using a plurality of beams for a single color plane. For example, in the case of the image forming apparatus for forming an image of each color plane by using two beams for a single color plane, in an image formed for each line in the main scanning direction, a first beam is used for exposure of odd-numbered lines in the sub scanning direction and a second beam is used for exposure of even-numbered lines. Due to this, it is made possible to increase the speed of image formation.
However, in the multibeam image forming apparatus, there is a case where the inclination and curve of the scanning line of each beam for a single color plane differ from beam to beam.